1. Field of the Invention
The present invention generally relates to the area of blood vessel graft systems. More particularly, the present invention provides a catheter base delivery device for deployment of multi-stage stented grafts comprising multiple coaxial delivery mechanisms. The coaxial delivery device enables the multiple stages of a stented graft to be assembled endovascularly.
2. Description of the Related Art
Aortic aneurysms are a common type of deteriorating disease caused by weakening of the wall of a blood vessel. The weakened wall, under the pressure of flowing blood, balloons outward. Such a deformity in the wall of a blood vessel not only affects its ability to conduct blood but is also potentially fatal if a rupture occurs at the site of the aneurysm.
Traditionally, the treatment for aneurysms entailed removing part or all of the aneurysm and implanting a replacement prosthetic section into the lumen. Alternatively, a synthetic or biomaterial graft is sutured end-to-end completely replacing the excised portion of the blood vessel. However, surgical treatment or removal of the aneurysm involves significant invasive techniques, extended hospitalization and associated risk of complications. Complications include extensive blood loss, respiratory tract infections, wound infections, and renal failure. In addition, the mortality rates (8%) are significant for such surgeries.
A more contemporary method of treatment of aneurysms is to place a graft within the lumen of the weakened blood vessel via a catheter based device. Conventional tubular aortic replacement sections, however, are generally larger in diameter than the femoral artery and therefore can not be inserted through the lumen of the femoral artery. The basic concept of a transluminal placement of an endovascular prosthesis for decreasing risk associated with the surgical repair of aortic aneurysms was proposed by Dotter (1969, Invest Radiol. 4:329-332). Since then, several investigators have studies the feasibility of different endovascular devices. For example Lazarus (U.S. Pat. No. 5,669,936) discloses a graft system having a capsule catheter that is deployed after femoral arteriotomy. To date, stent-grafts used clinically for treatment of abdominal and thoracic aortic aneurysms have required 18-F to 30-F delivery systems. The large size of the delivery system necessitated surgical femoral arteriotomy and sometimes retroperitoneal left iliac arteriotomy or distal aorta aortotomy, general anesthesia, and high levels of multidisciplinary cooperation. Occasionally, relatively healthy iliac vessels with large diameters are needed or in patients with highly sclerotic tortuous iliac arteries, angioplasty with or without stenting was necessary for performance of endovascular grafting. None of the clinically used devices is suitable for percutaneous insertion; all require a femoral arteriotomy because of their size.
Recently, a catheter based system for the delivery of grafts for repair of aortic aneurysms was disclosed in U.S. Pat. Nos. 5,713,917 and 5,591,195. The system includes a single stage graft comprised of two Nitinol springs. The two Nitinol springs are in physical communication with each other via a Nitinol connecting bar and are embedded in graft material at each end and covered completely by material so as to prevent direct exposure to bodily fluids or tissues. The graft is deployed by using an elongated sheath introducer having an axially extending sheath passage for receiving the graft and maintaining it in a compressed condition. A flexible push rod around the insertion catheter and within the sheath passage is used to push the graft out of the sheath during deployment.
In theory, one way to decrease the size of an endovascular device is to deploy the stented graft as separate parts. However, none of the delivery devices available are suitable for delivery of a multi-stage stented graft by a single percutaneous insertion. There is thus, an ongoing need for graft delivery devices for treatment of aneurysms which requires minimal preparation and hospitalization.